Composition policy takes child instance

The composition policy now takes a child instance instead
of the child type, as in all cases we have access to the child
object.

This allows new-style objects to be contained by old-style objects.

Updated all composition policies to use standardized argument names
instead of `context` and `candidate`; this makes it easier to
understand.

Updated AddActionProvider to hardcode the object types supported.

platform/entanglement/src/services/CopyService.js

@@ -48,7 +48,7 @@ define(
             return this.policyService.allow(
                 "composition",
                 parentCandidate.getCapability('type'),
-                object.getCapability('type')
+                object
             );
         };
 

platform/entanglement/src/services/LinkService.js

@@ -52,7 +52,7 @@ define(
             return this.policyService.allow(
                 "composition",
                 parentCandidate.getCapability('type'),
-                object.getCapability('type')
+                object
             );
         };
 

platform/entanglement/src/services/MoveService.js

@@ -56,7 +56,7 @@ define(
             return this.policyService.allow(
                 "composition",
                 parentCandidate.getCapability('type'),
-                object.getCapability('type')
+                object
             );
         };